A textbook on modal logic, intended for readers already acquainted with the elements of formal logic, containing nearly 500 exercises. Brian F. Chellas provides a systematic introduction to the principal ideas and results in contemporary treatments of modality, including theorems on completeness and decidability. Illustrative chapters focus on deontic logic and conditionality. Modality is a rapidly expanding branch of logic, and familiarity with the subject is now regarded as a necessary part of every philosopher's technical equipment. Chellas here offers an up-to-date and reliable guide essential for the student. A textbook, with exercises, on modal logic for readers already acquainted with the elements of formal logic. "Modal Logic" is a textbook on modal logic, intended for readers already acquainted with the elements of formal logic. Brian F. Chellas provides a systematic introduction to the principal ideas and results in contemporary treatments of modality, including theorems on completeness and decidability. Illustrative chapters focus on deontic logic and conditionality. There are nearly 500 exercises. This has been a rapidly expanding branch of logic over the last ten years, and familiarity with the subject is now regarded as a necessary part of every philosopher's technical equipment. Chellas here offers an up-to-date and reliable guide of the kind that is very badly needed: his exposition is distinguished by its clarity, economy and elegance, and the book is expected to supplant existing textbooks in the field. Used Book in Good Condition